Front panel description – MACKIE HR824 User Manual

Page 12

PWR

FRONT PANEL DESCRIPTION

Overload Protect

The high and low frequency power amplifiers

have clipping detectors that light the

OL LED

when either power amplifier output clips.
• If you see the

OL LED blinking more than

just occasionally, it’s an indication that you
should reduce the signal level coming from
your mixer or other signal source.

• If frequent clipping continues, the driver

thermal overload protection activates a
compressor that reduces the input level to
the amplifiers. During this time the

LED lights continuously.

• The compressor was designed to protect

the speakers and its action is highly
audible.

• The compressor was not designed for

mixing!

If a client insists on listening
to the monitors at a very high
volume, you may find that
the

OL LED lights frequently.

Since the majority of the

power requirement in any monitor are the low
frequencies, selectively reducing the low end
can provide a little more headroom and volume
for the monitors. Change the

LOW FREQ

switch to

47Hz or 80Hz, if necessary, to reduce

the bass response. This may allow the HR824s
to play just enough louder to satisfy the client
and to eliminate most of the amplifier clipping.

Power Switch

Use this switch to turn on or off the HR824

from the front. It works with the

POWER

MODE

switch on the rear panel in the

following way:
• If the

POWER MODE switch on the rear

panel is set to

STANDBY, the front panel

power

switch has no effect. The PWR

LED remains off.

• If the

POWER MODE switch is ON, the

front panel power switch turns the HR824
on or returns it to

STANDBY mode, as

indicated by the

PWR LED.

• If the

POWER MODE switch is in the

AUTO ON position, the front panel power
switch turns the HR824 on as long as there
is a signal present.

OL (Overload) LED

This LED blinks when the amplifiers begin

to clip and lights steadily if the overload protec-
tion circuit

has been triggered.

• Occasional blinking of the

OL LED indi-

cates that the loudest transients are
reaching the maximum output capability of
the amplifiers. This is okay.

• Frequent or continuous blinking of the

LED indicates that you have exceeded the
maximum output capability of the amplifi-
ers and that the amplifiers are clipping. If
you persist, the overload protection circuit
takes over, reducing the input level. You
should reduce the level from your signal
source until the

OL LED blinks occasionally

or not at all.

PROTECTION CIRCUITS

There are a number of protection mecha-

nisms designed into the HR824 to safeguard
the loudspeakers from inadvertent damage.

CAUTION: The protection circuits are de-

signed to prevent damage to the loudspeakers
under reasonable and sensible conditions.
Should you choose to ignore the warning signs
(i.e., frequent Overload LED indications, ex-
cessive distortion), you can still damage the
speakers in the HR824 by overdriving them
past the point of amplifier clipping. Such dam-
age is beyond the scope of the Warranty.